Bio-nano emulsion fuel

ABSTRACT

Disclosed herein is a method for synthesizing a nano-emulsion fuel composition. The method may include forming a water-in-fossil fuel emulsion by dispersing water into a fossil fuel in the presence of a surfactant, synthesizing carbon quantum dots with an average diameter between 0.5 nanometers to 20 nanometers, forming a mixture of the synthesized carbon quantum dots and the water-in-fossil fuel emulsion by dispersing the synthesized carbon quantum dots into the water-in-fossil fuel emulsion; the carbon quantum dots comprising 1 ppm to 10000 ppm of the mixture, and forming a nano-emulsion fuel composition by mixing a biofuel into the mixture of carbon quantum dots and the water-in-fossil fuel emulsion.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of priority from pending U.S.Provisional Patent Application Ser. No. 62/516,116, filed on Jun. 7,2017, and entitled “BIO-NANO EMULSION FUELS,” which is incorporatedherein by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to emulsified fuels, particularly tobio-nano emulsion fuels and methods of improving fuel combustion.

BACKGROUND

The high and growing costs of fossil fuels and the problem of depletionof these non-renewable resources has led to efforts for improving theefficiency of energy-consuming systems. Internal combustion engines thatare extensively used nowadays are one of the main consumers of fossilfuels. Most internal combustion engines produce undesirable pollutantsduring the combustion process. These undesirable pollutants are producedas a result of incomplete combustion, nitrogen separation, and presenceof impurities in the fossil fuels and air. Nitrogen oxides (NO_(x)),unburned hydrocarbons (HC), carbon oxides (CO_(x)), sulfur oxides(SO_(x)), soot, and other carbon particles are some of the moreimpactful pollutants emitted by the internal combustion engines. Thesepollutants have a negative impact on the environment and cause healthproblems including causing global warming, air pollution, acid rains,breathing problems, etc.

One possible solution to overcome the incomplete combustion process inthe internal combustion engines is the upgrading and improving of fuelcompositions. Instead of conducting cost prohibitive research onchanging the design of internal combustion engines, additives andcatalysts may be mixed in with fuel compositions to alter aspects of thecombustion process toward a more complete combustion reaction and moreefficient fuel consumption.

Different methods may be used for optimizing fuel consumption andreducing the emission of pollutants. For example, fuel-water emulsionsmay be prepared by mixing water into a fuel composition, which mayimprove combustion efficiency and pollutants emission. In anotherexample, nanotechnology may be utilized to enhance the properties of thefuel. Specifically, nano-additives can be used for lowering the amountof harmful pollutants emitted during the process of combustion andsimultaneously increase the efficiency of the combustion process.Different types of metal and metal oxide nanoparticles such as platinum,cobalt, radium, iridium, nickel, palladium, copper, silver, gold, zinc,aluminum, alumina, calcium oxide, titanium oxide, zirconium oxide, ironoxides, ruthenium oxide, osmium oxide, cobalt oxide, radium oxide,iridium oxide, nickel oxide, silver oxide, gold oxide, zinc oxide,cerium oxide etc. have been studied as additives in fossil fuels.However, there are some concerns regarding the potential harmful effectsof the nanoparticles on human health, especially in case of metal andmetal oxide nanoparticles. Since metal and metal oxide nanoparticles mayhave a poisonous impact on living organisms, there is a need in the artto find other biodegradable nano-additives, such as biodegradable carbonnanoparticles to optimize fuel consumption and reduce the emission ofpollutants minimizing any harmful impact on human health andenvironment.

SUMMARY

This summary is intended to provide an overview of the subject matter ofthe present disclosure, and is not intended to identify essentialelements or key elements of the subject matter, nor is it intended to beused to determine the scope of the claimed implementations. The properscope of the present disclosure may be ascertained from the claims setforth below in view of the detailed description below and the drawings.

According to one or more exemplary embodiments, the present disclosureis directed to a method for synthesizing a bio-nano emulsion fuelcomposition. The method may include forming a water-in-fossil fuelemulsion by dispersing water into a fossil fuel in the presence of asurfactant, synthesizing carbon quantum dots with an average diameterbetween 0.5 nanometers to 20 nanometers, forming a mixture of thesynthesized carbon quantum dots and the water-in-fossil fuel emulsion bydispersing the synthesized carbon quantum dots into the water-in-fossilfuel emulsion; the carbon quantum dots comprising 1 ppm to 100 ppm ofthe mixture, and forming a nano-emulsion fuel composition by mixing abiofuel into the mixture of carbon quantum dots and the water-in-fossilfuel emulsion.

According to some exemplary embodiments, synthesizing carbon quantumdots may include forming a precursor suspension by dissolving a carbonprecursor in water, the carbon precursor selected from the groupconsisting of graphene, graphene oxide, carbon nanotubes, fullerene,carbon nano-fibers, active carbon, soot, organic acids, and combinationsthereof, and forming carbon quantum dots by heating the precursorsuspension at a temperature between 160° C. and 220° C.

According to some exemplary embodiments, synthesizing carbon quantumdots may include forming a precursor suspension by dissolving a carbonprecursor in water, the carbon precursor selected from the groupconsisting of graphene, graphene oxide, carbon nanotubes, fullerene,carbon nano-fibers, active carbon, soot, organic acids, and combinationsthereof, forming carbon quantum dots by heating the precursor suspensionat a temperature between 160° C. and 220° C., carbonizing the carbonquantum dots at a temperature of at least 700° C. under an inert gasatmosphere, activating the carbonized carbon quantum dots by mixing thecarbonized carbon quantum dots with an alkali metal hydroxide solution,and functionalizing the activated carbon quantum dots by passing nitricacid vapor with a temperature between 100° C. and 150° C. through aheated bed of the activated carbon quantum dots, the heated bed beingheated at a temperature between 125° C. and 250° C.

According to an exemplary embodiment, forming a water-in-fossil fuelemulsion may include forming a water-in-fossil fuel emulsion bydispersing water into a fossil fuel in the presence of a surfactant, thewater comprising 0.01 to 50 vol % of the bio-nano emulsion fuelcomposition.

According to some exemplary embodiments, forming a bio-nano emulsionfuel composition by mixing a biofuel into the mixture of carbon quantumdots and the water-in-fossil fuel emulsion may include mixing thebiofuel into the mixture of carbon quantum dots and the water-in-fossilfuel emulsion, the biofuel comprising 0 to 99 vol % of the bio-nanoemulsion fuel composition.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawing figures depict one or more implementations in accord withthe present teachings, by way of example only, not by way of limitation.In the figures, like reference numerals refer to the same or similarelements.

FIG. 1 illustrates a method for synthesizing a bio-nano emulsion fuelcomposition, consistent with one or more exemplary embodiments of thepresent disclosure.

FIG. 2A illustrates method for synthesizing carbon quantum dots,consistent with one or more exemplary embodiments of the presentdisclosure.

FIG. 2B illustrates a method for synthesizing functionalized carbonquantum dots, consistent with one or more exemplary embodiments of thepresent disclosure.

FIG. 3 is a high-resolution transmission electron microscope (HR-TEM)image of the synthesized carbon quantum dots, consistent with one ormore exemplary embodiments of the present disclosure.

FIG. 4 illustrates an infrared spectrum of the synthesized carbonquantum dots, consistent with one or more exemplary embodiments of thepresent disclosure.

FIG. 5 is a high-resolution transmission electron microscope (HR-TEM)image of the synthesized functionalized carbon quantum dots, consistentwith one or more exemplary embodiment of the present disclosure.

FIG. 6 illustrates infrared spectrum of the synthesized functionalizedcarbon quantum dots, consistent with one or more exemplary embodimentsof the present disclosure.

FIG. 7 illustrates infrared spectrum of the synthesized functionalizedcarbon quantum dots, consistent with one or more exemplary embodimentsof the present disclosure.

FIG. 8 illustrates infrared spectrum of the synthesized functionalizedcarbon quantum dots, consistent with one or more exemplary embodimentsof the present disclosure.

FIG. 9 is a torque versus engine speed diagram for the one-cylinderdiesel engine burning four different fuel samples, consistent with oneor more exemplary embodiments of the present disclosure.

FIG. 10 is a specific fuel consumption (SFC) versus engine speed diagramfor the one-cylinder diesel engine burning four different fuel samples,consistent with one or more exemplary embodiments of the presentdisclosure.

FIG. 11 is an unburned hydrocarbon amount versus engine speed diagramfor the one-cylinder diesel engine burning four different fuel samples,consistent with one or more exemplary embodiments of the presentdisclosure.

FIG. 12 is a carbon monoxide amount versus engine speed diagram for theone-cylinder diesel engine burning four different fuel samples,consistent with one or more exemplary embodiments of the presentdisclosure.

FIG. 13 is a Nitrogen Oxide amount versus engine speed diagram for theone-cylinder diesel engine burning four different fuel samples,consistent with one or more exemplary embodiments of the presentdisclosure.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details are setforth by way of examples to provide a thorough understanding of therelevant teachings related to the exemplary embodiments. However, itshould be apparent that the present teachings may be practiced withoutsuch details. In other instances, well known methods, procedures,components, and/or circuitry have been described at a relativelyhigh-level, without detail, in order to avoid unnecessarily obscuringaspects of the present teachings.

The following detailed description is presented to enable a personskilled in the art to make and use the methods and devices disclosed inexemplary embodiments of the present disclosure. For purposes ofexplanation, specific nomenclature is set forth to provide a thoroughunderstanding of the present disclosure. However, it will be apparent toone skilled in the art that these specific details are not required topractice the disclosed exemplary embodiments. Descriptions of specificexemplary embodiments are provided only as representative examples.Various modifications to the exemplary implementations will be plain toone skilled in the art, and the general principles defined herein may beapplied to other implementations and applications without departing fromthe scope of the present disclosure. The present disclosure is notintended to be limited to the implementations shown, but is to beaccorded the widest possible scope consistent with the principles andfeatures disclosed herein.

Disclosed herein is a bio-nano emulsion fuel composition and method forsynthesizing the bio-nano emulsion fuel. Carbon quantum dots,functionalized carbon quantum dots, or a combination thereof aredispersed into the bio-nano emulsion fuel composition of exemplaryembodiments of the present disclosure to improve the combustion processof the fuel composition. The exemplary composition utilizes acombination of biodegradable carbon quantum dots, water, and biofuelsalongside the fossil fuel to ensure a complete fuel combustion processand thereby increase the efficiency of the fuel combustion process andreduce the production of pollutants. Furthermore, utilizing thebiodegradable carbon quantum dots helps avoid the toxicity of metal ormetal oxide nanoparticles while avoiding the costly synthesis methods ofother carbon nanoparticles.

FIG. 1 illustrates method 100 for synthesizing a bio-nano emulsion fuelcomposition, consistent with one or more exemplary embodiments of thepresent disclosure. Method 100 may include step 101 of forming awater-in-fossil fuel emulsion by dispersing water into a fossil fuel inthe presence of a surfactant, step 102 of synthesizing carbon quantumdots with an average diameter between 0.5 nanometers to 20 nanometers,step 103 of forming a mixture of the synthesized carbon quantum dots andthe water-in-fossil fuel emulsion by dispersing the synthesized carbonquantum dots into the water-in-fossil fuel emulsion, step 104 of forminga bio-nano emulsion fuel composition by mixing a biofuel into themixture of carbon quantum dots and the water-in-fossil fuel emulsion.

Referring to FIG. 1, according to one or more exemplary embodiments,step 101 of forming a water-in-fossil fuel emulsion by dispersing waterinto a fossil fuel in the presence of a surfactant may includedispersing water droplets into the fossil fuel in the presence ofsurfactants such as fatty acids. A fatty acid, such as oleic acid may bemixed with the water and the fossil fuel in a stirred vessel which isrigorously stirred with a stirrer speed of for example 500 rpm to 1000rpm. According to an exemplary embodiment, a first mixture may be formedby mixing the fossil fuel with oleic acid and mono ethanol amine in astirred vessel where a part of the oleic acid is neutralized and aneutral salt may form that functions as a hydrophilic agent, while theremaining oleic acid functions as a lipophilic agent in the firstmixture. Then fossil fuel, water, and a co-solvent such as n-Hexanol maybe mixed with the first mixture in the stirred vessel.

Referring to FIG. 1, according to an exemplary embodiment, step 101 offorming a water-in-fossil fuel emulsion by dispersing water into afossil fuel in the presence of a surfactant may include forming awater-in-diesel emulsion by dispersing water into diesel in the presenceof a fatty acid. In an example, to form every 100 mL of thewater-in-diesel emulsion, first 0.01 to 50 mL of the fatty acid and abalancing amount of mono ethanol amine may be stirred together in astirred vessel with a stirrer speed of 500 rpm to 1000 rpm for a periodof time between 1 to ten minutes. Then, 1 to 99 mL of diesel, 0.01 to 50mL of water, and 0.01 to 50 mL of a co-solvent such as n-Hexanol may beadded to the stirred vessel. After a stirring time of about 1 to 5minutes after diesel, water, and co-solvent are added to the stirredvessel, water droplets may be thoroughly dispersed inside the diesel anda clear and stable water-in-diesel emulsion may be obtained.

Referring to FIG. 1, according to one or more exemplary embodiments,step 102 of synthesizing carbon quantum dots with an average diameterbetween 0.5 nanometers to 20 nanometers may include synthesizing carbonquantum dots via either a top-down or a bottom-up synthesis route. Asused herein, the top-down synthesis route may involve breaking downlarger carbon structures such as graphite and carbon nanotubes intocarbon quantum dots using laser ablation, arc discharge, orelectrochemical methods. The bottom-up synthesis route may involvesynthesizing carbon quantum dots from small precursors such ascarbohydrates and citrate via, for example, a hydrothermal process.According to an exemplary embodiment, step 102 of synthesizing carbonquantum dots with an average diameter between 0.5 nanometers to 20nanometers may include synthesizing carbon quantum dots from a precursorby a hydrothermal process. The precursor may be selected from carbonprecursors such as graphene, graphene oxide, carbon nanotubes,fullerene, carbon nano-fibers, active carbon, soot, organic acids (e.g.,sucrose, glucose, citric acid, etc.) and natural precursors like treeleaves, fruit marc, fruit juice, fruit skin, soya, egg, sugar caneextract, gelatin, chitosan, etc.

FIG. 2A illustrates a method 200 for synthesizing carbon quantum dotswith an average diameter between 0.5 nanometers to 20 nanometers,consistent with one or more exemplary embodiments of the presentdisclosure. Method 200 is an exemplary embodiment of step 102 of method100. Referring to FIG. 2A, method 200 may include step 201 of forming aprecursor suspension by dissolving a carbon precursor in water, and step202 of forming carbon quantum dots by heating the precursor suspensionat a temperature between 160° C. and 220° C. According to an embodiment,method 200 may further include an optional step of drying the formedcarbon quantum dots at a temperature of at least 80° C.

Referring to FIG. 2A, according to an exemplary embodiment, step 201 offorming a precursor suspension by dissolving a carbon precursor in watermay include forming a precursor suspension by dissolving citric acid andurea in water with citric acid:urea:water ratio of 1:3:5. According toanother exemplary embodiment, step 202 of forming carbon quantum dots byheating the precursor suspension at a temperature between 160° C. and220° C. may include heating the precursor suspension at a temperaturebetween 160° C. and 220° C. for at least 4 hours.

FIG. 2B is a method 210 for synthesizing functionalized carbon quantumdots with an average diameter between 0.5 nanometers to 20 nanometers,consistent with one or more exemplary embodiments of the presentdisclosure. Method 210 is another exemplary embodiment of step 102 ofmethod 100. Referring to FIG. 2B, method 210 may include step 203 offorming a precursor suspension by dissolving a carbon precursor inwater, step 204 of forming carbon quantum dots by heating the precursorsuspension at a temperature between 160° C. and 220° C., step 205 ofcarbonizing the carbon quantum dots at a temperature of at least 700° C.under an inert gas atmosphere, step 206 of activating the carbonizedcarbon quantum dots by mixing the carbonized carbon quantum dots with analkali metal hydroxide solution, and step 207 of functionalizing theactivated carbon quantum dots by passing nitric acid vapor with atemperature between 100° C. and 150° C. through a heated bed of theactivated carbon quantum dots.

Referring to FIG. 2B, according to an exemplary embodiment, step 203 offorming a precursor suspension by dissolving a carbon precursor in watermay be similar to step 201 of FIG. 2A and step 204 of forming carbonquantum dots by heating the precursor suspension at a temperaturebetween 160° C. and 220° C. may be similar to step 202 of FIG. 2A.

Referring to FIG. 2B, according to an exemplary embodiment, step 205 ofcarbonizing the carbon quantum dots at a temperature of at least 700° C.under an inert gas atmosphere may include heating the carbon quantumdots at a temperature between 600° C. and 900° C. under nitrogen orargon atmosphere. According to an exemplary embodiment, carbonizing thecarbon quantum dots at a temperature of at least 700° C. under an inertgas atmosphere may include heating the carbon quantum dots in a heatingsystem such as a furnace at a temperature of at least 700° C. undernitrogen or argon atmosphere for at least 1 hour.

Referring to FIG. 2B, according to an exemplary embodiment, step 206 ofactivating the carbonized carbon quantum dots by mixing the carbonizedcarbon quantum dots with an alkali metal hydroxide solution may includemixing the carbonized carbon quantum dots with an alkali metal hydroxidesolution and then heating the mixture of the carbonized carbon quantumdots and the alkali metal hydroxide solution at 800° C. under a nitrogenor argon atmosphere for at least 1 hour. According to an exemplaryembodiment, the carbonized carbon quantum dots may be mixed with analkali metal hydroxide solution such as a KOH solution with a(carbonized carbon quantum dots:KOH) ratio of 1:1.5 to 2:3.

With reference to FIG. 2B, according to some exemplary embodiments, step207 of functionalizing the activated carbon quantum dots by passingnitric acid vapor with a temperature between 100° C. and 150° C. througha heated bed of the activated carbon quantum dots may include forming abed of the activated carbon quantum dots, heating the formed bed of theactivated carbon quantum dots by, for example, a heating element at atemperature between 125° C. and 250° C., passing a vapor stream ofnitric acid through the bed of the activated carbon quantum dots byheating concentrated nitric acid at a temperature between 100° C. and150° C. in a vessel and then guiding the produced nitric acid vaporthrough the bed of the activated carbon quantum dots. According to anexemplary embodiment, functionalizing the activated carbon quantum dotsby passing nitric acid vapor with a temperature between 100° C. and 150°C. through a heated bed of the activated carbon quantum dots may includepassing nitric acid vapor with a temperature between 100° C. and 150° C.through a heated bed of the activated carbon quantum dots for apredetermined amount of time between 2 and 24 hours, and then cuttingoff the vapor stream of nitric acid and leaving the bed of nowfunctionalized carbon quantum dots to dry. With respect to step 207, theactivated carbon quantum dots may be functionalized with functionalgroups of hydroxyl and carboxyl.

Referring back to FIG. 1, according to some exemplary embodiments, step103 may involve forming a mixture of the synthesized carbon quantum dotsand the water-in-fossil fuel emulsion by dispersing the synthesizedcarbon quantum dots into the water-in-fossil fuel emulsion. According toan exemplary embodiment, dispersing the synthesized carbon quantum dotsinto the water-in-fossil fuel emulsion may include adding thesynthesized carbon quantum dots with a predetermined concentrationbetween 1 ppm and 10000 ppm to the water-in-fossil fuel emulsion andthen dispersing the synthesized carbon quantum dots into thewater-in-fossil fuel emulsion by ultrasonic waves. Due to the small sizeof the synthesized carbon quantum dots, which may be between 0.5 nm and20 nm, and functional groups on the carbon quantum dots, such asoxygen-containing functional groups, the synthesized carbon quantum dotsmay be thoroughly dispersed into the water-in-fossil fuel emulsion.According to an exemplary embodiment, forming a mixture of thesynthesized carbon quantum dots and the water-in-fossil fuel emulsion bydispersing the synthesized carbon quantum dots into the water-in-fossilfuel emulsion may include dispersing about 1 ppm to 10000 ppm of thesynthesized carbon quantum dots into a water-in-diesel emulsion. To thisend, ultrasonic waves may be applied to a mixture of 1 ppm to 10000 ppmof the synthesized carbon quantum dots and the water-in-diesel emulsionfor at least 1 minute.

With reference to FIG. 1, according to some exemplary embodiments, step104 may involve forming a bio-nano emulsion fuel composition by mixing abiofuel into the mixture of carbon quantum dots and the water-in-fossilfuel emulsion. The biofuel may be easily mixed into the fossil fuelphase of the mixture of carbon quantum dots and the water-in-fossil fuelemulsion. According to an exemplary embodiment, mixing a biofuel intothe mixture of carbon quantum dots and the water-in-fossil fuel emulsionmay include mixing a biodiesel into the mixture of carbon quantum dotsand the water-in-diesel emulsion such that the biodiesel may comprise[0] to [99] vol % of the a bio-nano emulsion fuel composition.

Example 1 Synthesizing Carbon Quantum Dots with Urea and Citric Acid asPrecursors

In this example, carbon quantum dots are synthesized by a hydrothermalmethod with urea and citric acid as precursors. To this end, an initialprecursor including 0.21 grams of citric acid and 0.18 grams of urea wasdissolved in 5 grams of water to obtain a first solution. The firstsolution was then transferred into an autoclave and underwent ahydrothermal process in the autoclave at 160° C. for 4 hours. Theresultant solution was then removed from the autoclave and was dried at80° C. and about 0.4 grams of carbon quantum dots were synthesized perevery gram of the initial precursor. As-prepared carbon quantum dots arereferred to hereinafter as CQDs.

FIG. 3 is a high-resolution transmission electron microscope (HR-TEM)image of the synthesized CQDs, consistent with one or more exemplaryembodiments of the present disclosure. Referring to FIG. 3, the averagesize of the synthesized CQDs is less than 20 nm.

FIG. 4 illustrates an infrared spectrum of the synthesized CQDs,consistent with one or more exemplary embodiments of the presentdisclosure. Referring to FIG. 4 the broad absorption peak observed in3100-3500 cm⁻¹ region is indicative of the presence of OH groups relatedto HO—C═O and/or C—OH; of course, the N—H tensile absorption alsooverlaps in this region. The characteristic absorption of C—O, C—N, andCH₂ emerges in 1403 cm⁻¹, 1169 cm⁻¹ and 1323 cm⁻¹, respectively. Thepeaks observed in 1575 cm⁻¹ and 894 cm⁻¹ result from tensile absorptionsrelated to C═C. The tensile and flexural vibrations special for bondsbetween carbon and the heteroatom is observed in the structure ofsynthesized CQDs due to the presence of functional groups of oxygen andnitrogen in the structure of synthesized CQDs.

According to one or more exemplary embodiments of the presentdisclosure, a bio-nano emulsion fuel composition synthesized by method100 of FIG. 1 may include 0 to 99 vol % of a fossil fuel such as dieseloil, gasoline, ethanol, methanol or combinations thereof, 0 to 99 vol %of a biofuel such as biodiesel, bioethanol or combinations thereof, 0.01to 50 vol % of water, and 1 to 10000 ppm of carbon quantum dots withaverage diameters between 0.5 nm to 20 nm. According to an exemplaryembodiment, the bio-nano emulsion fuel may include 0 to 99 vol % ofdiesel, 0 to 99 vol % of biodiesel, 0.01 to 50 vol % water, and 1 to 100ppm of carbon quantum dots with average diameters between 0.5 nm to 20nm.

Example 2 Synthesizing Functionalized Carbon Quantum Dots with Urea andCitric Acid as Precursors

In this example, functionalized carbon quantum dots are synthesized by ahydrothermal method with urea and citric acid as precursors. To thisend, an initial precursor including 0.21 grams of citric acid and 0.18grams of urea was dissolved in 5 grams of water to obtain a secondsolution. The second solution was then transferred into an autoclave andunderwent a hydrothermal process in the autoclave at 160° C. for 4hours. The resultant solution was then removed from the autoclave andwas dried at 80° C. to obtain the synthesized carbon quantum dots. Thesynthesized carbon quantum dots were then carbonized at 700° C. under aninert gas atmosphere for 1 hour. The carbonized carbon quantum dots werethen activated by homogeneously mixing the carbonized carbon quantumdots with an alkali metal hydroxide solution, such as KOH with a KOH tocarbonized quantum dots ratio (KOH:carbonized quantum dots) of about2:3, and then applying heat treatment to the homogeneous solution of thecarbonized carbon quantum dots and KOH at a temperature of 800° C. for 1hour. The activated carbon quantum dots may then be functionalized byforming a bed of the activated carbon quantum dots that is heated at atemperature of 125° C. to 250° C.; passing a vapor of concentratednitric acid with a temperature between 100° C. and 150° C. through thebed of the activated carbon quantum dots for at most 24 hours. Theobtained functionalized carbon quantum dots are hereinafter referred toas CQD-Fs.

FIG. 5 is a high-resolution transmission electron microscope (HR-TEM)image of the synthesized CQD-Fs, consistent with one or more exemplaryembodiment of the present disclosure. Referring to FIG. 5, the averagesize of the synthesized CQD-Fs is less than 20 nm.

FIG. 6 illustrates infrared spectrum of the synthesized CQD-Fs.Referring to FIG. 6, the wide absorption peak observed in 3200-3500 cm⁻¹region is indicative of the existence of OH groups related to HO—C═Oand/or C—OH. The peak observed in 1608 cm⁻¹ arises from aromatic bondsof C═C indicating the carbon structure. Also, the absorption peaksobserved in 1716 cm⁻¹ and 1384 cm⁻¹ show C—O and CH₃ bonds,respectively. Furthermore, the absorption peak in 1218 cm⁻¹ is theresult of the presence of C—H and N—H bonds.

Example 3 Synthesizing Carbon Quantum Dots with Orange Peel as aPrecursor

In this example, carbon quantum dots are synthesized by a hydrothermalmethod with orange peel as a precursor. To this end, 1 to 12 grams ofpowdered orange peel was mixed with 120 mL of deionized water. Theobtained solution was then transferred to an autoclave where ahydrothermal process was applied to the obtained solution at 140° C. to220° C. for 10 to 24 hours. After removing the resultant solution fromthe autoclave, the resultant solution was centrifuged with a speed of5000 rpm to separate an upper solution from sediments. The separatedupper solution contained carbon quantum dots which were later dried at80° C. to 120° C. The as-produced carbon quantum dots are hereinafterreferred to as CQD-Os.

FIG. 7 illustrates infrared spectrum of the synthesized f CQD-Os.Referring to FIG. 7, the presence of functional groups on thesynthesized CQD-Os. The absorption peak observed in 1601 cm⁻¹ is theevidence for the presence of C═C bond. Also, two other absorption peaksin the region of 1600-1680 cm⁻¹ are indicative of the presence of C═Cand C═N bonds; that's because of the characteristic peaks of the abovebonds overlapping with each other. The absorption peaks appearing in3414 cm⁻¹, 2929 cm⁻¹, 1386 cm⁻¹, 1281 cm⁻¹, and 1100 cm⁻¹ show thepresence of OH, C—H, C—H, C—O, and C—O on the synthesized CQD-Os,respectively. As a result, the functional groups are present in thestructure of CQD-Os due to the bond of carbon structure with nitrogen,hydrogen, and oxygen atoms.

Example 4 Synthesizing Carbon Quantum Dots with Olive Kernel as aPrecursor

In this example, carbon quantum dots are synthesized by a hydrothermalmethod with orange peel as a precursor. To this end, 1 to 12 grams ofmilled olive kernel was mixed with 120 mL of deionized water. Theobtained solution was then transferred to an autoclave where ahydrothermal process was applied to the obtained solution at 160° C. to220° C. for 10 to 24 hours. After removing the resultant solution fromthe autoclave, the resultant solution was centrifuged with a speed of5000 rpm to separate an upper solution from sediments. The separatedupper solution contained carbon quantum dots which were later dried at80° C. to 120° C. The as-produced carbon quantum dots are hereinafterreferred to as CQD-Hs.

FIG. 8 illustrates infrared spectrum of the synthesized CQD-Hs.Referring to FIG. 8, the absorption band in 1605 cm⁻¹ region is relatedto C═C vibration with sp² hybridization. The absorption peak in 3423cm⁻¹ region is the evidence for the presence of OH groups related toC—OH and/or HO—C═O. The C—H characteristic absorption has appeared in2934 cm⁻¹, 1384 cm⁻¹, and 803 cm⁻¹ regions, while C—O vibrations areevident in 1110 cm⁻¹ region.

Example 5 Synthesizing Bio-Nano Emulsion Fuel Sample B15+W10+CQD

In this example, bio-nano emulsion fuel samples are synthesized thatcontain diesel as the fossil fuel, biodiesel as the biofuel, carbonquantum dots, and water. Here, for synthesizing a 100 mL of a bio-nanoemulsion fuel sample, a first mixture is formed by mixing 7 mL of afatty acid, such as oleic acid, and 0.7 mL of mono ethanol amine in astirred vessel with a stirrer speed of 500 to 1000 rpm. Then, 81.3 mL ofdiesel fuel, 10 mL of water, and 1 mL of a co-solvent such as n-Hexanolare added to the first mixture and after 1 to 5 minutes of stirring,water droplets are thoroughly dispersed inside the continuous phase ofthe diesel fuel and a clear and stable water-in-diesel fuel emulsion isformed. After that, 60 ppm of carbon quantum dots or graphene quantumdots are added to the water-in-diesel fuel emulsion while being exposedto ultrasonic waves in an ultrasound device for 1 minute. Due to theirsmall size and many functional groups, carbon quantum dots are easilydispersed into the water droplets present in the water-in-diesel fuelemulsion and a clear second mixture is formed. At this stage, thebio-nano emulsion fuel sample is formed by mixing 15% by volume of abiodiesel with the second mixture. The biodiesel is easily mixed withthe continuous diesel phase of the second mixture.

Example 6 Synthesizing Bio-Nano Emulsion Fuel Sample B15+W5+CQD

In this example, bio-nano emulsion fuel samples are synthesized thatcontain diesel as the fossil fuel, biodiesel as the biofuel, carbonquantum dots, and water. Here, for synthesizing a 100 mL of a bio-nanoemulsion fuel sample (a diesel fuel containing 5% water), first, 4 mL ofa fatty acid such as oleic acid and 0.4 mL of mono ethanol amine weremixed in a stirred vessel with a stirrer speed of 500 to 1000 rpm. Then,89.1 mL of diesel fuel, 5 mL of water, and 1.5 mL of a co-solvent suchas n-Hexanol are added to the first mixture and after 1 to 5 minutes ofstirring, water droplets are thoroughly dispersed inside the continuousphase of the diesel fuel and a clear and stable water-in-diesel fuelemulsion is formed. After that, 60 ppm of carbon quantum dots orgraphene quantum dots are added to the water-in-diesel fuel emulsionwhile being exposed to ultrasonic waves in an ultrasound device for 1minute. Due to their small size and many functional groups, quantum dotsare easily dispersed into the water droplets present in thewater-in-diesel fuel emulsion and a clear second mixture is formed. Atthis stage, the bio-nano emulsion fuel sample is formed by mixing 15% byvolume of a biodiesel with the second mixture. The biodiesel is easilymixed with the continuous diesel phase of the second mixture.

Example 7 Synthesizing Bio-Nano Emulsion Fuel Sample B15+W5+CQD-F

In this example, bio-nano emulsion fuel samples are synthesized thatcontain diesel as the fossil fuel, biodiesel as the biofuel, carbonquantum dots, and water. Here, for synthesizing a 100 mL of a bio-nanoemulsion fuel sample (a diesel fuel containing 5% water), at first 4 mLof a fatty acid such as oleic acid and 0.4 mL of mono ethanol amine weremixed in a stirred vessel with a stirrer speed of 500 to 1000 rpm. Then,89.1 mL of diesel fuel, 5 mL of water, and 1.5 mL of a co-solvent suchas n-Hexanol are added to the first mixture and after 1 to 5 minutes ofstirring, water droplets are thoroughly dispersed inside the continuousphase of the diesel fuel and a clear and stable water-in-diesel fuelemulsion is formed. After that, 60 ppm of functionalized carbon quantumdots (CQD-F) is added to the water-in-diesel fuel emulsion while beingexposed to ultrasonic waves in an ultrasound device for 1 minute. Due totheir small size and many functional groups, quantum dots are easilydispersed into the water droplets present in the water-in-diesel fuelemulsion and a clear second mixture is formed. At this stage, thebio-nano emulsion fuel sample is formed by mixing 15% by volume of abiodiesel with the second mixture. The biodiesel is easily mixed withthe continuous diesel phase of the second mixture.

Example 8 Synthesizing Fuel Sample B15+W5

In this example, emulsion fuel samples are synthesized that containdiesel as the fossil fuel, biodiesel as the biofuel, and water. Here,for synthesizing a 100 mL of a bio-nano emulsion fuel sample (a dieselfuel containing 5% water), at first 4 mL of a fatty acid such as oleicacid and 0.4 mL of mono ethanol amine were mixed in a stirred vesselwith a stirrer speed of 500 to 1000 rpm. Then, 89.1 mL of diesel fuel, 5mL of water, and 1.5 mL of a co-solvent such as n-Hexanol are added tothe first mixture and after 1 to 5 minutes of stirring, water dropletsare thoroughly dispersed inside the continuous phase of the diesel fueland a clear and stable water-in-diesel fuel emulsion is formed. Afterthat, the emulsion fuel sample is formed by mixing 15% by volume of abiodiesel with the second mixture. The biodiesel is easily mixed withthe continuous diesel phase of the second mixture.

Example 9 Synthesizing Fuel Sample B15

In this example, bio-fuel samples are synthesized that contain diesel asthe fossil fuel and biodiesel as the biofuel. Here, for synthesizing a100 mL of a B15 sample (a diesel fuel containing 15% biodiesel), 15 mLbiodiesel is added to the 85 mL of diesel fuel and after a littlestirring, biodiesel mixed with the diesel fuel and a clear and stablebio-fuel is formed. The biodiesel is easily mixed with the continuousdiesel phase of the diesel fuel.

Example 10 Synthesizing Fuel Sample B15+W5+CQD-H

In this example, bio-nano emulsion fuel samples are synthesized thatcontain diesel as the fossil fuel, biodiesel as the biofuel, carbonquantum dots, and water. Here, for synthesizing a 100 mL of a bio-nanoemulsion fuel sample (a diesel fuel containing 5% water), at first 4 mLof a fatty acid such as oleic acid and 0.4 mL of mono ethanol amine weremixed in a stirred vessel with a stirrer speed of 500 to 1000 rpm. Then,89.1 mL of diesel fuel, 5 mL of water, and 1.5 mL of a co-solvent suchas n-Hexanol are added to the first mixture and after 1 to 5 minutes ofstirring, water droplets are thoroughly dispersed inside the continuousphase of the diesel fuel and a clear and stable water-in-diesel fuelemulsion is formed. After that, 60 ppm of carbon quantum dots (CQD-H) isadded to the water-in-diesel fuel emulsion while being exposed toultrasonic waves in an ultrasound device for 1 minute. Due to theirsmall size and many functional groups, carbon quantum dots are easilydispersed into the water droplets present in the water-in-diesel fuelemulsion and a clear second mixture is formed. At this stage, thebio-nano emulsion fuel sample is formed by mixing 15% by volume of abiodiesel with the second mixture. The biodiesel is easily mixed withthe continuous diesel phase of the second mixture.

Example 11 Effects of Synthesized Fuel Samples on a Diesel EnginePerformance

The effect of synthesized fuel samples on the performance parameters ofa diesel engine is investigated in this example. The performanceparameters of the diesel engine may include torque and specific fuelconsumption. Specific fuel consumption (SFC) is the mass rate of thefuel consumed for the generation of one kilowatt-hour actual work by thediesel engine. A one-cylinder diesel engine connected to an Eddy-CurrentDynamometer was used to test the synthesized fuel samples. The samplesincluded a pure diesel fuel, B15 fuel sample, B15+W5 fuel sample, andB15+W5+CQD bio-nano emulsion fuel sample.

FIG. 9 is a torque versus engine speed diagram for the one-cylinderdiesel engine burning four different fuel samples. Referring to FIG. 9,torque versus speed diagram 901 is obtained for the one-cylinder dieselengine burning the diesel fuel; torque versus speed diagram 902 isobtained for the one-cylinder diesel engine burning the B15 fuel sample;torque versus speed diagram 903 is obtained for the one-cylinder dieselengine burning the B15+W5 fuel sample; and torque versus speed diagram904 is obtained for the one-cylinder diesel engine burning theB15+W5+CQD bio-nano emulsion fuel sample.

Referring to FIG. 9, comparing torque versus speed diagram 901 andtorque versus speed diagram 902 shows that the torque of the engineburning the B15 fuel sample is lower than that of the diesel engineburning the pure diesel fuel, which means the addition of the biodieselto the diesel fuel reduces the engine torque. This may be due to thelower heat value of a biodiesel fuel compared to a diesel fuel.Comparing torque versus speed diagram 903 and torque versus speeddiagram 902 shows that the torque of the diesel engine burning theB15+W5 sample is higher than that of the engine burning the B15 sample,which means by the addition of 5% water to B15 fuel sample, the amountof initial power reduction is compensated which can be the result of thephenomenon of micro-explosion of water particles leading to improvedcombustion. Comparing torque versus speed diagram 904 and torque versusspeed diagram 901 shows that the torque of the diesel engine burning theB15+W5+CQD bio-nano emulsion fuel sample is considerably higher thanthat of the diesel engine burning the pure diesel fuel.

FIG. 10 is an SFC versus engine speed diagram for the one-cylinderdiesel engine burning four different fuel samples. Referring to FIG. 10,SFC versus speed diagram 1001 is obtained for the one-cylinder dieselengine burning the diesel fuel; SFC versus speed diagram 1002 isobtained for the one-cylinder diesel engine burning the B15 fuel sample;SFC versus speed diagram 1003 is obtained for the one-cylinder dieselengine burning the B15+W5 fuel sample; and SFC versus speed diagram 1004is obtained for the one-cylinder diesel engine burning the B15+W5+CQDbio-nano emulsion fuel sample. The results show that the SFC of thediesel engine has the lowest value when the B15+W5+CQD bio-nano emulsionfuel sample is burnt in the diesel engine. Referring to FIGS. 9 and 10,the results show that the addition of carbon quantum dot to the fuelcomposition improves both the torque and SFC performance of a dieselengine.

Example 12 Effects of Synthesized Fuel Samples on Pollutant Emission ofa Diesel Engine

Production of unburned or incompletely burned hydrocarbons like carbonmonoxide is the result of incomplete combustion in an internalcombustion engine. Unburned hydrocarbons are considered as pollutants.

FIG. 11 is an unburned hydrocarbon amount versus engine speed diagramfor the one-cylinder diesel engine burning four different fuel samples.Referring to FIG. 11, unburned hydrocarbon amount versus speed diagram1101 is obtained for the one-cylinder diesel engine burning the dieselfuel; unburned hydrocarbon amount versus speed diagram 1102 is obtainedfor the one-cylinder diesel engine burning the B15 fuel sample; unburnedhydrocarbon amount versus speed diagram 1103 is obtained for theone-cylinder diesel engine burning the B15+W5 fuel sample; and unburnedhydrocarbon amount versus speed diagram 1104 is obtained for theone-cylinder diesel engine burning the B15+W5+CQD-Fnano emulsion fuelsample. Referring to FIG. 11, the results show that the addition ofcarbon quantum dot to the fuel composition reduces the unburnedhydrocarbon emission of the tested diesel engine by 30 to 57 percent atdifferent engine speeds.

Carbon monoxide is a colorless, odorless, and very dangerous gas thatmay be produced during an incomplete process of combustion. The emissionof carbon monoxide may depend on air to fuel ratio.

FIG. 12 is a carbon monoxide amount versus engine speed diagram for theone-cylinder diesel engine burning four different fuel samples.Referring to FIG. 12, carbon monoxide amount versus speed diagram 1201is obtained for the one-cylinder diesel engine burning the diesel fuel;carbon monoxide amount versus speed diagram 1202 is obtained for theone-cylinder diesel engine burning the B15 fuel sample; carbon monoxideamount versus speed diagram 1203 is obtained for the one-cylinder dieselengine burning the B15+W5 fuel sample; and carbon monoxide amount versusspeed diagram 1204 is obtained for the one-cylinder diesel engineburning the B15+W5+CQD bio-nano emulsion fuel sample. Referring to FIG.12, the results show that the addition of carbon quantum dot to the fuelcomposition reduces the carbon monoxide emission of the tested dieselengine by 9 to 33 percent at different engine speeds.

The nitrogen oxides produced in the exhaust pipe of internal combustionengines are a combination of nitric oxide (NO) and nitrogen dioxide(NO₂). In fact, nitrogen and oxygen react at high temperature at aspecific ratio and produce NOx compounds.

FIG. 13 is a NO_(x) amount versus engine speed diagram for theone-cylinder diesel engine burning four different fuel samples.Referring to FIG. 13, NO_(x) amount versus speed diagram 1301 isobtained for the one-cylinder diesel engine burning the diesel fuel;NO_(x) amount versus speed diagram 1302 is obtained for the one-cylinderdiesel engine burning the B15 fuel sample; NO_(x) amount versus speeddiagram 1303 is obtained for the one-cylinder diesel engine burning theB15+W5 fuel sample; and NO_(x) amount versus speed diagram 1304 isobtained for the one-cylinder diesel engine burning the B15+W5+CQDbio-nano emulsion fuel sample. Referring to FIG. 13, the results showthat the addition of carbon quantum dot to the fuel composition reducesthe NO_(x) emission of the tested diesel engine by 25 to 41 percent atdifferent engine speeds.

While the foregoing has described what are considered to be the bestmode and/or other examples, it is understood that various modificationsmay be made therein and that the subject matter disclosed herein may beimplemented in various forms and examples, and that the teachings may beapplied in numerous applications, only some of which have been describedherein. It is intended by the following claims to claim any and allapplications, modifications and variations that fall within the truescope of the present teachings.

Unless otherwise stated, all measurements, values, ratings, positions,magnitudes, sizes, and other specifications that are set forth in thisspecification, including in the claims that follow, are approximate, notexact. They are intended to have a reasonable range that is consistentwith the functions to which they relate and with what is customary inthe art to which they pertain.

The scope of protection is limited solely by the claims that now follow.That scope is intended and should be interpreted to be as broad as isconsistent with the ordinary meaning of the language that is used in theclaims when interpreted in light of this specification and theprosecution history that follows and to encompass all structural andfunctional equivalents. Notwithstanding, none of the claims are intendedto embrace subject matter that fails to satisfy the requirement ofSections 101, 102, or 103 of the Patent Act, nor should they beinterpreted in such a way. Any unintended embracement of such subjectmatter is hereby disclaimed.

Except as stated immediately above, nothing that has been stated orillustrated is intended or should be interpreted to cause a dedicationof any component, step, feature, object, benefit, advantage, orequivalent to the public, regardless of whether it is or is not recitedin the claims.

It will be understood that the terms and expressions used herein havethe ordinary meaning as is accorded to such terms and expressions withrespect to their corresponding respective areas of inquiry and studyexcept where specific meanings have otherwise been set forth herein.Relational terms such as first and second and the like may be usedsolely to distinguish one entity or action from another withoutnecessarily requiring or implying any actual such relationship or orderbetween such entities or actions. The terms “comprises,” “comprising,”or any other variation thereof, are intended to cover a non-exclusiveinclusion, such that a process, method, article, or apparatus thatcomprises a list of elements does not include only those elements butmay include other elements not expressly listed or inherent to suchprocess, method, article, or apparatus. An element proceeded by “a” or“an” does not, without further constraints, preclude the existence ofadditional identical elements in the process, method, article, orapparatus that comprises the element.

The Abstract of the Disclosure is provided to allow the reader toquickly ascertain the nature of the technical disclosure. It issubmitted with the understanding that it will not be used to interpretor limit the scope or meaning of the claims. In addition, in theforegoing Detailed Description, it can be seen that various features aregrouped together in various implementations. This is for purposes ofstreamlining the disclosure, and is not to be interpreted as reflectingan intention that the claimed implementations require more features thanare expressly recited in each claim. Rather, as the following claimsreflect, inventive subject matter lies in less than all features of asingle disclosed implementation. Thus, the following claims are herebyincorporated into the Detailed Description, with each claim standing onits own as a separately claimed subject matter.

While various implementations have been described, the description isintended to be exemplary, rather than limiting and it will be apparentto those of ordinary skill in the art that many more implementations andimplementations are possible that are within the scope of theimplementations. Although many possible combinations of features areshown in the accompanying figures and discussed in this detaileddescription, many other combinations of the disclosed features arepossible. Any feature of any implementation may be used in combinationwith or substituted for any other feature or element in any otherimplementation unless specifically restricted. Therefore, it will beunderstood that any of the features shown and/or discussed in thepresent disclosure may be implemented together in any suitablecombination. Accordingly, the implementations are not to be restrictedexcept in light of the attached claims and their equivalents. Also,various modifications and changes may be made within the scope of theattached claims.

What is claimed is:
 1. A method for synthesizing a bio-nano emulsionfuel composition, the method comprising: forming a water-in-fossil fuelemulsion by dispersing water into a fossil fuel in the presence of asurfactant; synthesizing carbon quantum dots with an average diameterbetween 0.5 nanometers and 20 nanometers, synthesizing carbon quantumdots comprising: forming a precursor suspension by dissolving a carbonprecursor in water, the carbon precursor one of graphene, grapheneoxide, carbon nanotubes, fullerene, carbon nano-fibers, active carbon,soot, organic acids, and combinations thereof; and forming carbonquantum dots by heating the precursor suspension at a temperaturebetween 160° C. and 220° C.; carbonizing the carbon quantum dots at atemperature of at least 700° C. under an inert gas atmosphere;activating the carbonized carbon quantum dots by mixing the carbonizedcarbon quantum dots with an alkali metal hydroxide solution; andfunctionalizing the activated carbon quantum dots by passing nitric acidvapor with a temperature between 100° C. and 150° C. through a heatedbed of the activated carbon quantum dots, the heated bed being heated ata temperature between 125° C. and 250° C.; forming a mixture of thesynthesized carbon quantum dots and the water-in-fossil fuel emulsion bydispersing the synthesized carbon quantum dots into the water-in-fossilfuel emulsion, the carbon quantum dots comprising 1 ppm to 100 ppm ofthe mixture; and forming a bio-nano emulsion fuel composition by mixinga biofuel into the mixture of carbon quantum dots and thewater-in-fossil fuel emulsion.
 2. A method for synthesizing a bio-nanoemulsion fuel composition, the method comprising: forming awater-in-fossil fuel emulsion by dispersing water into a fossil fuel inthe presence of a surfactant; synthesizing carbon quantum dots with anaverage diameter between 0.5 nanometers and 20 nanometers; forming amixture of the synthesized carbon quantum dots and the water-in-fossilfuel emulsion by dispersing the synthesized carbon quantum dots into thewater-in-fossil fuel emulsion, the carbon quantum dots comprising 1 ppmto 100 ppm of the mixture; and forming a bio-nano emulsion fuelcomposition by mixing a biofuel into the mixture of carbon quantum dotsand the water-in-fossil fuel emulsion.
 3. The method according to claim2, wherein synthesizing carbon quantum dots includes: forming aprecursor suspension by dissolving a carbon precursor in water, thecarbon precursor one of graphene, graphene oxide, carbon nanotubes,fullerene, carbon nano-fibers, active carbon, soot, organic acids, andcombinations thereof; and forming carbon quantum dots by heating theprecursor suspension at a temperature between 160° C. and 220° C.
 4. Themethod according to claim 3, further comprising: carbonizing the carbonquantum dots at a temperature of at least 700° C. under an inert gasatmosphere; activating the carbonized carbon quantum dots by mixing thecarbonized carbon quantum dots with an alkali metal hydroxide solution;and functionalizing the activated carbon quantum dots by passing nitricacid vapor with a temperature between 100° C. and 150° C. through aheated bed of the activated carbon quantum dots, the heated bed beingheated at a temperature between 125° C. and 250° C.
 5. The methodaccording to claim 4, wherein carbonizing the carbon quantum dots at atemperature of at least 700° C. under an inert gas atmosphere includesheating the carbon quantum dots in a heating system at a temperature ofat least 700° C. under an inert gas atmosphere for at least 1 hour. 6.The method according to claim 4, wherein activating the carbonizedcarbon quantum dots comprises: mixing the carbonized carbon quantum dotswith an alkali metal hydroxide solution; and heating the mixture of thecarbonized carbon quantum dots and the alkali metal hydroxide solutionat a temperature of at least 800° C. for at least 1 hour.
 7. The methodaccording to claim 6, wherein mixing the carbonized carbon quantum dotswith an alkali metal hydroxide solution includes mixing the carbonizedcarbon quantum dots with an alkali metal hydroxide solution with a(carbonized carbon quantum dots: alkali metal hydroxide solution) ratiobetween 1:1.5 and 2:3.
 8. The method according to claim 4, whereinfunctionalizing the activated carbon quantum dots includes passingnitric acid vapor with a temperature between 100° C. and 150° C. througha heated bed of the activated carbon quantum dots for 2 to 24 hours. 9.The method according to claim 3, wherein forming carbon quantum dots byheating the precursor suspension includes forming carbon quantum dots byheating the precursor suspension at a temperature between 160° C. and220° C. for at least 4 hours.
 10. The method according to claim 3,wherein forming a precursor suspension by dissolving the carbonprecursor in water comprises forming a precursor suspension bydissolving citric acid and urea in water.
 11. The method according toclaim 2, wherein forming a water-in-fossil fuel emulsion includesforming a water-in-fossil fuel emulsion by dispersing water into afossil fuel in presence of a surfactant, the water comprising 0.01 to 50vol % of the nano-emulsion fuel composition.
 12. The method according toclaim 2, wherein forming a nano-emulsion fuel composition by mixing abiofuel into the mixture of carbon quantum dots and the water-in-fossilfuel emulsion includes mixing the biofuel into the mixture of carbonquantum dots and the water-in-fossil fuel emulsion, the biofuelcomprising 0 to 99 vol % of the nano-emulsion fuel composition.